Back in the very early 1960s, Tony Hoare proposed adding implicit type rules to ALGOL. The ALGOL committee boxed his ears, HARD. Requiring variables to be declared explicitly was known, EVEN THEN, shown to reduce errors in programming.

Tony mentioned this in his Turing talk, as I recall, and said it was BEFORE the probably-apocryphal Venus probe FORTRAN story, where a typo in a FORTRAN DO-statement instead created a brand-new variable and assigned it a value. Various versions of that story float around: the most credible one says that it was caught in a review, and, if it had not been caught, would have resulted in the total loss of a (very expensive) spacecraft.

This was some 50 years ago.

In 1963, Tony Hoare proposed adding implicit type rules to ALGOL. The ALGOL committee boxed his ears, HARD. Requiring variables to be declared explicitly was known, EVEN THEN, shown to reduce errors in programming.

Tony mentioned this in his Turing talk, and said it was BEFORE the probably-apocryphal Venus probe FORTRAN story, where a typo in a FORTRAN DO-statement instead created a brand-new variable and assigned it a value. Various versions of that story float around: the most credible one says that it was caught in a review, and, if it had not been caught, would have resulted in the total loss of a (very expensive) spacecraft.

This was 53 years ago.